Foam used in a heat insulator of a heat-insulating housing of a refrigerator or the like is made of a foamed resin such as urethane foam, and chlorofluorocarbons conventionally have been used as a foaming gas therefor. Since chlorofluorocarbons may destroy the ozone layer, it is necessary to collect them and prevent them from diffusing into the air at the time of disposing of the foam.
A conventional method for collecting a foaming gas from foam will be described by way of an exemplary method for disassembling a discarded refrigerator.
First, a refrigerant (for example, chlorofluorocarbons) and a refrigeration oil are collected from the discarded refrigerator, and then a compressor is removed (a pretreatment process). The resultant heat-insulating housing of the refrigerator is put into a peeling and smashing machine (a rough smashing process). The peeling and smashing machine includes a rotating cylindrical body having many rotating and projecting blades on its outer periphery. The peeling and smashing machine roughly smashes the heat-insulating housing of the refrigerator into pieces having a size on the order of several cm and separates the outer wall material (steel plate), the inner wall material (resin plate), the linear object and the heat insulator (urethane foam). At this time, some of the closed-cells in the heat insulator are destroyed, thus releasing the chlorofluorocarbons. These chlorofluorocarbons are collected by equipment for collecting low-concentration chlorofluorocarbons.
The steel plate, the resin plate, the linear object and the foamed resin that have been smashed roughly are fractionated by a wind-power separator utilizing the difference in specific gravity or the like.
The fractionated foamed resin is sent to a crusher and smashed further minutely, so that remaining chlorofluorocarbons are drawn out (a minute crushing process). As a method for collecting the chlorofluorocarbons for this case, a method described in JP 2679562 B is known, for example. After the foamed resin is smashed roughly into pieces having a size on the order of several cm, it is put into a hopper and sent to the crusher. In the process where an external mechanical force is applied in the crusher so as to crush the foamed resin, closed-cells therein are destroyed. Chlorofluorocarbons released from the closed-cells and the minutely crushed resin grains are sent to a bag filter together with the air, so that a gaseous component and the resin grains are separated. When the resin grains are heated and compressed in a volume reducer, any remaining chlorofluorocarbons are squeezed out also at this time.
Together with the air, the chlorofluorocarbons generated in the above processes are introduced into a container filled with activated carbon (adsorbent), thus allowing a rare chlorofluorocarbon component in the air to be once adsorbed in the activated carbon. Then, this activated carbon is heated to release chlorofluorocarbons, thereby taking out chlorofluorocarbons with a relatively high concentration. The air containing these concentrated chlorofluorocarbons is passed through a cooling device, so that the chlorofluorocarbons are liquefied and collected. The chlorofluorocarbons that have not been adsorbed in the activated carbon in the above description and the chlorofluorocarbons that have not been liquefied and separated in the cooling process are sent back to the hopper together with the air. In this manner, the chlorofluorocarbons contained in the foam can be separated and collected without being diffused into the air.
However, the above-described disassembling method has had the following problems.
In the rough smashing process and the minute crushing process, since the chlorofluorocarbons released from the foam into the air and solid materials are fractionated by a wind-power separating method, the concentration of chlorofluorocarbons is extremely low.
Because chlorofluorocarbons have a low boiling point, in order to cool down and liquefy rare chlorofluorocarbons directly without any adsorbing and releasing process by the activated carbon, it is essential to cool them down to an extremely low temperature that is considerably lower than −40° C., as becomes clear from a vapor pressure curve shown in FIG. 14. As a result, large-scale and expensive cooling equipment is needed.
Accordingly, by concentrating chlorofluorocarbons through the adsorbing and releasing process using the activated carbon, the cooling temperature at the time of liquefying and collecting has been shifted to a higher side.
However, a large amount of the activated carbon is needed for adsorbing chlorofluorocarbons, and it is necessary to cool down or heat the large amount of the activated carbon having a low thermal conductivity to a temperature suitable for adsorbing and releasing. This takes a considerably long time. Also, for an actual continuous operation, it is necessary to prepare a plurality of containers filled with the activated carbon and switch them for the adsorbing and releasing, which results in still larger equipment.
As described above, the conventional method for collecting chlorofluorocarbons is extremely inefficient because the chlorofluorocarbons diffused in an extremely low concentration are once condensed using the activated carbon and then cooled down so as to be liquefied and separated. Furthermore, the equipment for carrying out these processes is large, raising equipment costs and operation costs considerably and impairing profitability seriously.